[gnome-shell-extensions/gnome-3-0] Fix a local null pointer dereference and a return causing a null pointer dereference in the caller w

[Giovanni Campagna <gcampagna src gnome org>]

commit 825903f8fc30d75a49428a04ea57fbdc8978331a
Author: Lance <windchine gmail com>
Date:   Sat Nov 26 07:33:02 2011 +0000

    Fix a local null pointer dereference and a return causing a null pointer dereference in the caller when alt-tab used with no windows open in any workspace in the current gnome-shell session.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=663064
    
    https://bugzilla.gnome.org/show_bug.cgi?id=664409

 extensions/alternate-tab/extension.js |   11 ++++++++---
 1 files changed, 8 insertions(+), 3 deletions(-)
---
diff --git a/extensions/alternate-tab/extension.js b/extensions/alternate-tab/extension.js
index 0e158c4..8ae0d5c 100644
--- a/extensions/alternate-tab/extension.js
+++ b/extensions/alternate-tab/extension.js
@@ -60,8 +60,11 @@ AltTabPopup2.prototype = {
 	}
 	normal_windows.sort(Lang.bind(this, this._sortWindows));
 
-        let win_on_top = normal_windows.shift();
-        normal_windows.push(win_on_top);
+        if(normal_windows.length) {
+            let win_on_top = normal_windows.shift();
+            normal_windows.push(win_on_top);
+        }
+
 	windows = normal_windows;
 	for (let w = 0; w < windows.length; w++) {
 	    let win = windows[w];
@@ -78,8 +81,10 @@ AltTabPopup2.prototype = {
 	    appIcons.push(ap1); 
 	}
 
-        if (!windows.length)
+        if (!windows.length) {
+            this.destroy();
             return false;
+        }
 
         if (!Main.pushModal(this.actor))
             return false;